Power tool with compact motor assembly

ABSTRACT

A power tool includes a housing and a brushless motor with a rotor and a stator assembly. The motor defines a motor envelope bounded by a rear plane at a rearmost point of the stator assembly and rotor, a front plane at a frontmost point of the stator assembly and rotor, and a generally cylindrical boundary surrounding a radially outermost portion of the stator assembly and rotor. A rotor shaft is rotatably driven by the rotor. A transmission includes an input member rotatably driven by the rotor shaft and an output member. A first bearing supporting the rotor shaft is at least partially received within the motor envelope. A second bearing supporting the rotor shaft or a component of the transmission is at least partially received within the motor envelope. A support plate supporting a component of the transmission may be at least partially received within the motor envelope.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 62/950,409 filed Dec. 19, 2019, content of which isincorporated herein by reference in its entirety.

FIELD

This disclosure relates to a power tool, such as an impact driver orimpact wrench, with a compact motor assembly, such as a low-profile andcompact brushless motor assembly.

BACKGROUND

Power tools such as impact drivers and impact wrenches may be used fordriving threaded fasteners into workpieces. Such power tools may lacksufficient power to drive a threaded fastener into a workpiece or may betoo large in length or girth to fit into a desired location. In suchpower tools, it is desirable to reduce the girth and/or length of thetool, including the motor assembly and related components, withoutsacrifice power performance.

SUMMARY

In a first aspect, a power tool includes a housing having a rearward endportion and a forward end portion and a brushless motor received in thehousing. The motor includes a rotor configured to rotate about a rotoraxis and a stator assembly having a stator core and conductive windings.The motor defines a motor envelope bounded by a rear plane at a rearmostpoint of the stator assembly and the rotor, a front plane at a frontmostpoint of the stator assembly and the rotor, and a generally cylindricalboundary extending from the rear plane to the front plane andsurrounding a radially outermost portion of the stator assembly and therotor. A rotor shaft extends along the rotor axis and is coupled to andconfigured to be rotatably driven by rotation of the rotor. Atransmission is received in the housing and includes an input membercoupled to and configured to be rotatably driven by rotation of therotor shaft, and an output member configured to be driven by rotation ofthe input member. A first bearing is configured to support the rotorshaft and is at least partially received within the motor envelope. Asecond bearing is configured to support a component of the transmissionand is at least partially received within the motor envelope.

In a second aspect, a power tool includes a housing having a rearwardend portion and a forward end portion and a brushless motor received inthe housing. The motor includes a rotor configured to rotate about arotor axis and a stator assembly having a stator core and conductivewindings. A rotor shaft extends along the rotor axis and is coupled toand configured to be rotatably driven by rotation of the rotor. Atransmission is received in the housing and includes an input membercoupled to and configured to be rotatably driven by rotation of therotor shaft. An output member is configured to be driven by rotation ofthe input member. A first bearing is configured to support the rotorshaft and at least partially nested inside the stator assembly. A secondbearing is configured to support a component of the transmission and atleast partially nested inside the stator assembly.

Implementations of the first and second aspects may include one or moreof the following features. The stator may at least partially surroundthe rotor. The input member may comprise a gear rotatably driven by therotor shaft. The transmission may comprise a planetary gear set with theinput member including a sun gear rotatably driven by the rotor shaft,the output member including a carrier, and the planetary gear setfurther including a planet gear rotatably mounted to the carrier andmeshed with the sun gear and a ring gear meshed with the planet gear andheld non-rotatably relative to the housing. The second bearing may beconfigured to support the carrier. The second bearing may be configuredto support the sun gear. The second bearing may be configured to supportthe output member and may further comprise a third bearing configured tosupport the rotor shaft. The rearward end portion of the housing mayinclude a rear cap defining a recess and the third bearing may bedisposed at least partially in the recess. A fan may be coupled to therotor shaft. The fan may be disposed between the stator and the rear endwall. The fan may include a hub and a vane portion extending radiallyoutward from the hub. The hub may be at least partially received in thestator assembly.

A support plate may be configured to support at least a portion of thetransmission and held non-rotatably relative to the housing. The supportplate may include a nested portion at least partially received withinthe motor envelope. The nested portion of the support plate may supportthe first bearing. The nested portion of the support plate may supportthe second bearing. The nested portion of the support plate may includea rearward projection of the support plate. The nested portion may be atleast partially received within the stator. The nested portion may be atleast partially received within a recess in the rotor. The first bearingmay be nested at least partially within at least a portion of the rotor.The rotor may define a central recess and the first bearing may bereceived at least partially within the recess.

An output spindle may have a front end proximal a front end portion ofthe housing and a rotational impact mechanism coupled to the outputmember of the transmission and to the output spindle. The impactmechanism may be configured to transmit continuous rotary motion withoutimpacts from the transmission to the output spindle when a torque on theoutput spindle does not exceed a transition torque, and to transmitrotational impacts from the motor to the output spindle when a torque onthe output spindle exceeds the transition torque. The mechanism mayinclude a cam shaft extending forward from the output member, a hammerreceived over the cam shaft and configured to move axially androtationally relative to the cam shaft, a spring disposed between thehammer and the output member and configured to bias the hammer away fromthe cam shaft, and an anvil coupled to the output spindle, the hammerconfigured to transmit continuous rotary motion to the anvil when thetorque on the output spindle does not exceed a transition torque and thehammer configured to apply rotational impacts to the anvil when thetorque on the output spindle exceeds a transition torque.

The power tool may have a maximum power output of at least 430 Watts anda length of the tool from a rear end of the housing to a front end ofthe output spindle of less than or equal to 110 mm. A ratio of themaximum power output of the motor to the length of the tool may be atleast 4.5 Watts/mm. The power tool may have a maximum output torque ofat least 1820 inch-pounds and a length of the tool from a rear end ofthe housing to a front end of the output spindle is less than or equalto 110 mm. A ratio of the maximum output torque of the tool to thelength of the tool may be at least 18.0 inch-pounds/mm.

In a third aspect, a power tool includes a housing having a rearward endportion, a forward end portion, and defining a tool axis. A brushlessmotor is received in the housing. The motor includes a rotor configuredto rotate about a rotor axis and a stator assembly having a stator coreand conductive windings. A rotor shaft extends along the rotor axis andis configured to be rotatably driven by rotation of the rotor. Atransmission is received in the housing and includes an input memberconfigured to be rotatably driven by rotation of the rotor shaft and anoutput member configured to be driven by rotation of the input member.An output spindle has a front end proximate the front end portion of thehousing. A rotational impact mechanism is coupled to the output memberof the transmission and to the output spindle. The impact mechanism isconfigured to transmit continuous rotary motion without impacts from thetransmission to the output spindle when a torque on the output spindledoes not exceed a transition torque, and to transmit rotational impactsfrom the motor to the output spindle when a torque on the output spindleexceeds the transition torque. A ratio of maximum power output to alength of the tool from a rear end of the housing to a front end of theoutput spindle is at least 4.5 Watts/mm.

In a fourth aspect, a power tool includes a housing having a rearwardend portion, a forward end portion, and defining a tool axis. Abrushless motor is received in the housing. The motor includes a rotorconfigured to rotate about a rotor axis and a stator assembly having astator core and conductive windings. A rotor shaft extends along therotor axis and is configured to be rotatably driven by rotation of therotor. A transmission is received in the housing and includes an inputmember configured to be rotatably driven by rotation of the rotor shaftand an output member configured to be driven by rotation of the inputmember. An output spindle has a front end proximate the front endportion of the housing. A rotational impact mechanism is coupled to theoutput member of the transmission and to the output spindle. The impactmechanism is configured to transmit continuous rotary motion withoutimpacts from the transmission to the output spindle when a torque on theoutput spindle does not exceed a transition torque, and to transmitrotational impacts from the motor to the output spindle when a torque onthe output spindle exceeds the transition torque. A ratio of a maximumoutput torque of the tool to a length of tool from a rear end of thehousing to a front end of the output spindle is at least 18.0inch-pounds/mm.

Implementations of the third and fourth aspects may include one or moreof the following features. The stator may at least partially surroundthe rotor. The input member may comprise a gear rotatably driven by therotor shaft. The transmission may comprise a planetary gear set with theinput member including a sun gear rotatably driven by the rotor shaft,the output member including a carrier, and the planetary gear setfurther including a planet gear rotatably mounted to the carrier andmeshed with the sun gear and a ring gear meshed with the planet gear andheld non-rotatably relative to the housing. A first bearing may beconfigured to support the motor output shaft and may be at leastpartially nested within the stator assembly. A second bearing may beconfigured to support at least one of the rotor shaft and a portion ofthe transmission. At least a portion of the second bearing may be nestedwithin the stator assembly. The second bearing may be configured tosupport the rotor shaft. A third bearing may be configured to supportthe input member of the transmission. The second bearing may beconfigured to support the input member of the transmission. The thirdbearing may be configured to support the rotor shaft. The third bearingmay be positioned rearward of the stator. The housing may include a rearend wall with a recess and the third bearing may be disposed at leastpartially in the recess.

A fan may be coupled to the rotor shaft. The fan may be disposed betweenthe stator and the rear end cap. The rotor may define a central recessand the first bearing may be received at least partially within therecess. A support plate may be configured to support at least a portionof the transmission and held non-rotatably relative to the housing. Thesupport plate may be at least partially received within the stator. Thesupport plate may support a first bearing that supports the rotor shaftand a second bearing that supports at least one of the rotor shaft and aportion of the transmission. The support plate may have a rearwardprojection that is at least partially received within a recess in therotor.

The impact mechanism may include a cam shaft extending forward from theoutput member, a hammer received over the cam shaft and configured tomove axially and rotationally relative to the cam shaft, a springdisposed between the hammer and the output member and configured to biasthe hammer away from the cam shaft, and an anvil coupled to the outputspindle, the hammer configured to transmit continuous rotary motion tothe anvil when the torque on the output spindle does not exceed atransition torque and the hammer configured to apply rotational impactsto the anvil when the torque on the output spindle exceeds a transitiontorque. The power tool may have a maximum power output of at least 430Watts and a length of the tool from a rear end of the housing to a frontend of the output spindle may be less than or equal to 110 mm. The powertool may have a maximum output torque of at least 1820 inch-pounds and alength of the tool from a rear end of the housing to a front end of theoutput spindle of less than or equal to 110 mm.

In a fifth aspect, a power tool includes a housing having a rear endportion and a front end portion and a brushless motor received in thehousing. The motor includes a rotor configured to rotate about a rotoraxis and a stator assembly having a stator core and conductive windings.The motor defines a motor envelope bounded by a rear plane at a rearmostpoint of the stator assembly and the rotor, a front plane at a frontmostpoint of the stator assembly and the rotor, and a generally cylindricalboundary extending from the rear plane to the front plane andsurrounding a radially outermost portion of the stator assembly and therotor. A rotor shaft extends along the rotor axis and is coupled to andconfigured to be rotatably driven by rotation of the rotor. Atransmission is received in the housing and includes an input memberconfigured to be rotatably driven by rotation of the rotor shaft, and anoutput member configured to be driven by rotation of the input member. Asupport plate is configured to support at least a portion of thetransmission, where the support plate is held non-rotatably relative tothe housing and has a rearward portion at least partially receivedwithin the motor envelope.

In a sixth aspect, a power tool includes a housing having a rear endportion and a front end portion and a brushless motor received in thehousing. The motor includes a rotor configured to rotate about a rotoraxis and a stator assembly having a stator core and conductive windings.A rotor shaft extends along the rotor axis and is coupled to andconfigured to be rotatably driven by rotation of the rotor. Atransmission is received in the housing and includes an input memberconfigured to be rotatably driven by rotation of the rotor shaft, and anoutput member configured to be driven by rotation of the input member. Asupport plate is configured to support at least a portion of thetransmission, where the support plate is held non-rotatably relative tothe housing and has a rearward portion at least partially nested withinthe stator assembly.

In a seventh aspect, a power tool includes a power tool includes ahousing having a rear end portion and a front end portion and abrushless motor received in the housing. The motor includes a rotorconfigured to rotate about a rotor axis and a stator assembly having astator core and conductive windings. A rotor shaft extends along therotor axis and is coupled to and configured to be rotatably driven byrotation of the rotor. A transmission is received in the housing andincludes an input member configured to be rotatably driven by rotationof the rotor shaft, and an output member configured to be driven byrotation of the input member. A support plate is configured to supportat least a portion of the transmission, where the support plate is heldnon-rotatably relative to the housing and has a rearward portion atleast partially received within the rotor.

Implementations of the fifth, sixth, and seventh aspects may include oneor more of the following features. The stator may at least partiallysurround the rotor. The input member may comprise a gear rotatablydriven by the rotor shaft. A first bearing may be configured to supportthe rotor shaft and a second bearing may be configured to support one ofthe rotor shaft and a portion of the transmission. Each of the firstbearing and the second bearing may be at least partially received in thestator assembly. The transmission may include a planetary gear set withthe input member including a sun gear rotatably driven by the rotorshaft, the output member including a carrier, and the planetary gear setfurther including a planet gear rotatably mounted to the carrier andmeshed with the sun gear and a ring gear meshed with the planet gear andheld non-rotatably relative to the housing.

The second bearing may be configured to support the carrier. The secondbearing is may be configured to support the sun gear. The second bearingmay be configured to support the rotor shaft. The second bearing may beconfigured to support the output member of the transmission. A thirdbearing may be configured to support the rotor shaft. The rearward endportion of the housing may include a rear cap defining a recess and thethird bearing may be disposed at least partially in the recess. A fanmay be coupled to the rotor shaft. The fan may be disposed between thestator and the rear end wall. The fan may include a hub and a vaneportion extending radially outward from the hub, the hub being at leastpartially received in the stator assembly. The first bearing may benested at least partially within at least a portion of the rotor. Therotor may define a central recess and the first bearing may be receivedat least partially within the recess.

An output spindle may have a front end proximal a front end portion ofthe housing and a rotational impact mechanism coupled to the outputmember of the transmission and to the output spindle. The impactmechanism may be configured to transmit continuous rotary motion withoutimpacts from the transmission to the output spindle when a torque on theoutput spindle does not exceed a transition torque, and to transmitrotational impacts from the motor to the output spindle when a torque onthe output spindle exceeds the transition torque. The impact mechanismmay include a cam shaft extending forward from the output member, ahammer received over the cam shaft and configured to move axially androtationally relative to the cam shaft, a spring disposed between thehammer and the output member and configured to bias the hammer away fromthe cam shaft, and an anvil coupled to the output spindle, the hammerconfigured to transmit continuous rotary motion to the anvil when thetorque on the output spindle does not exceed a transition torque and thehammer configured to apply rotational impacts to the anvil when thetorque on the output spindle exceeds a transition torque.

The power tool may have a maximum power output of at least 430 Watts anda length of the tool from a rear end of the housing to a front end ofthe output spindle may be less than or equal to 110 mm. a ratio of themaximum power output of the motor to the length of the tool may be atleast 4.5 Watts/mm. The power tool may have a maximum output torque ofat least 1820 inch-pounds and a length of the tool from a rear end ofthe housing to a front end of the output spindle of less than or equalto 110 mm. A ratio of the maximum output torque of the tool to thelength of the tool is at least 18.0 inch-pounds/mm.

Advantages may include one or more of the following. At least a portionof each of a motor bearing and a second bearing that supports a portionof the transmission or the rotor shaft is received in the motor envelopeand at least partially nested within the stator assembly, reducing theoverall length of the power tool along the tool axis. Also, at least aportion of at least one of the motor bearings and/or the transmissionbearing is received in and nested within the rotor, reducing the overalllength of the power tool. In addition, at least a portion of the supportplate 130 is received in and nested within the stator assembly and therotor, reducing the overall length of the power tool. At the same time,the power tool may be configured to produce a maximum power output of atleast approximately 450 Watts and a maximum output torque of at leastapproximately 1800 inch-pounds. Thus, the power tool is able to producemuch greater power and torque than would be expected in an impact powertool of comparable size (e.g., a ratio of power output to tool length ofat least approximately 4.5 Watts/mm and/or a ratio of output torque totool length of at least approximately 18.0 inch-pounds/mm. These andother features and advantages will become apparent and within the scopeof this application.

According to an aspect of this disclosure, a power tool is providedincluding a tool housing, a support plate provided within the toolhousing, a rear tool cap mounted on a rear end of the tool housing. anda brushless direct-current (BLDC) motor received within the housing. TheBLDC motor includes a stator assembly including a stator core, statorteeth radially extending from the stator core and defining slotstherebetween, and stator windings wound around the stator teeth. TheBLDC motor further includes a rotor shaft extending along a longitudinalaxis, a front motor bearing mounted on the rotor shaft and supported bythe support plate, a rear motor bearing mounted on the rotor shaft andsupported by the rear tool cap, and a rotor. The rotor includes a rotorcore mounted on the rotor shaft within the stator assembly and a magnetring mounted around the rotor core. The rotor core defines an annularrecess within which at portion of the front bearing and a portion of thesupport plate are located such that the a radial plane intersects thefront bearing, the magnet ring, and the stator core.

In an embodiment, the magnet ring includes a sintered permanent magnet.

In an embodiment, rotor core includes at least two alignment rings on anouter surface thereof defining one or more annular grooves therebetween.In an embodiment, an adhesive is provided within the annular grooves tosecure the magnet ring to the rotor core.

In an embodiment, the rotor core includes at least two axial pads on anouter surface thereof defining one or more axial channels therebetween.In an embodiment, an adhesive is provided within the axial channels tosecure the magnet ring to the rotor core.

In an embodiment, the support plate includes a radial wall providedadjacent the stator assembly, a bearing pocket formed at a centerportion of the radial wall to receive the front motor bearing, and astator piloting feature extending from the radial wall to engage aportion of the stator assembly to radially support the support platerelative to the stator assembly.

In an embodiment, the stator piloting feature includes axial postsaxially extending from the radial wall around the bearing pocket intothe slots of the stator assembly in engagement with at least one of thestator core or tip portions of the stator teeth to radially support thesupport plate relative to the stator assembly.

In an embodiment, a transmission assembly is disposed forward of theBLDC motor, and the support plate includes a radial wall providedadjacent the stator assembly, a first bearing pocket formed at a centerportion of a first surface of the radial wall received within theannular recess of the rotor core and configured to receive the frontmotor bearing, and a second bearing pocket formed on a second surface ofthe radial wall facing the transmission assembly and configured toreceive a component of the transmission assembly.

In an embodiment, the BLDC motor further includes a terminal blockarranged on an outer surface of the stator core intersecting the radialplane, the terminal block including terminals each extending parallel tothe longitudinal axis and each including a tang portion to which atleast one of the stator windings is connected.

In an embodiment, the BLDC motor further includes a circuit board onwhich at least one magnetic sensor is mounted to magnetically sense themagnet ring, where the circuit board is oriented along a second radialplane that intersects the stator windings.

In an embodiment, a fan is mounted on the rotor shaft, and an innerportion of the fan is recessed to allow the rear bearing to be radiallyaligned with at least a portion of the fan.

In an embodiment, the rear tool cap includes a radial body that includesa central bearing pocket arranged to receive the rear motor bearing, aperipheral portion extending form the radial body arranged to be matewith the tool housing, and at least one constraining member projectingfrom the radial body to engage the stator assembly and radially securethe stator assembly relative to the rear tool cap independently of thetool housing.

In an embodiment, the rear tool cap is integrally formed as a part ofthe tool housing.

According to another aspect of this disclosure, a brushlessdirect-current (BLDC) motor is provided including a stator assembly. Thestator assembly includes a stator core, stator teeth radially extendingfrom the stator core and defining slots therebetween, and statorwindings wound around the stator teeth. The motor further includes arotor shaft that extends along a longitudinal axis and a rotor includinga rotor core mounted on the rotor shaft, a permanent magnet ring mountedon an outer surface of the rotor core, and an adhesive material disposedbetween the rotor core and the permanent magnet ring. The rotor coreincludes a first portion having an outer diameter that substantiallycorresponds to an inner diameter of the permanent magnet ring to allowthe first portion of the rotor core to be form-fittingly received withinthe permanent magnet ring in direct contact therewith and to radiallysecure the permanent magnet ring to the stator core, and a secondportion having an outer diameter that is smaller than the inner diameterof the permanent magnet ring. The adhesive material is disposed betweenthe second portion of the rotor core and the permanent magnet ring toaxially secure the permanent magnet ring to the stator core.

In an embodiment, the first portion of the rotor core includes at leasttwo annular alignment rings and the second portion of the rotor coreincludes at least one annular groove formed between the at least twoannular alignment rings. In an embodiment, the adhesive material isdisposed within the annular groove.

In an embodiment, the first portion of the rotor core includes at leastone annular axial pad and the second portion of the rotor core includesat least one axial channel. In an embodiment, the adhesive material isdisposed within the at least one axial channel.

In an embodiment, the permanent magnet ring includes a sintered magnet.

In an embodiment, the rotor core defines an annular recess within whichat portion of a bearing of the rotor shaft is located.

In an embodiment, the rotor core includes uniformly shaped laminationsbonded together and shaped to form the first portion and the secondportion of the rotor core.

In an embodiment, the rotor core includes a first set of laminationsshaped to form the first portion of the rotor core and a second set oflaminations shaped to form the second portion of the rotor core.

In an embodiment, a power tool is provided including a tool housing abrushless direct-current (BLDC) motor as described above received withinthe housing.

According to another embodiment, a brushless direct-current (BLDC) motoris provided including a stator assembly. The stator assembly includes astator core, stator teeth radially extending from the stator core anddefining slots therebetween, and stator windings wound around the statorteeth. The motor further includes a rotor shaft that extends along alongitudinal axis and a rotor including a rotor core mounted on therotor shaft, a permanent magnet ring mounted on an outer surface of therotor core, and an adhesive material disposed between the rotor core andthe permanent magnet ring. In an embodiment, the rotor core includesannular grooves formed in the outer surface within which the adhesivematerial is disposed to axially secure the permanent magnet ring to thestator core.

In an embodiment, the rotor core has an outer diameter thatsubstantially corresponds to an inner diameter of the permanent magnetring to allow the rotor core to be form-fittingly received within thepermanent magnet ring in direct contact therewith and to radially securethe permanent magnet ring to the stator core.

In an embodiment, the rotor core has an outer diameter that is smallerthan an inner diameter of the permanent magnet ring to form a gap withinwhich the adhesive material is received.

In an embodiment, a power tool provided including a tool housing and aBLDC motor as described disposed within the housing.

According to another aspect of this disclosure, a brushlessdirect-current (BLDC) motor is provided including a stator assemblyincluding a stator core, stator teeth radially extending from the statorcore and defining slots therebetween, and stator windings wound aroundthe stator teeth; a rotor shaft extending along a longitudinal axis; anda rotor including a rotor core mounted on the rotor shaft. The rotorcore supports at least one permanent magnet that magnetically interactswith the stator windings to cause a rotation of the rotor relative tothe stator assembly. A circuit board is provided having a main body andat least one leg radially projecting from the main body to support atleast one magnetic sensor in close proximity to the at least onepermanent magnet. In an embodiment, the leg is oriented along a radialplane that intersects the stator windings.

In an embodiment, the stator assembly further includes an end insulatormounted on an end surface of the stator core to insulate the stator corefrom the stator windings. In an embodiment, the circuit board is mountedand fastened to the end insulator.

In an embodiment, the circuit board at least three legs radiallyprojecting from the main body to support three magnetic sensors. In anembodiment, each leg extends between two adjacent stator windings in thedirection of the rotor towards a center of the stator assembly.

In an embodiment, each of the three magnetic sensors is substantiallycircumferentially aligned with inner portions of the stator windings.

In an embodiment, the main body of the circuit board includes a firstportion that is curved and extends along the end of the stator assemblybut does not extend peripherally beyond an outer surface of the statorcore, and a second portion that extends peripherally beyond the outersurface of the stator core and through which at least one fastener isprovided to secure the circuit board to the end insulator.

In an embodiment, a connector is mounted on the second portion of themain body of the circuit board and signal wires are coupled to theconnector.

In an embodiment, the fastener is peripherally provided beyond the outersurface of the stator core.

In an embodiment, a retention feature provided on the first portion ofthe main body of the circuit board and arranged to make a mechanicalconnection with a portion of the end insulator, wherein no portion ofthe retention feature projects over a rear surface of the circuit boardin a direction opposite the stator core.

In an embodiment, the second portion covers an angular distance in therange of approximately 60 degrees to 90 degrees.

In an embodiment, the first portion is provided within a part of themain body of the circuit board that covers an angular distance in therange of approximately 35 degrees to 55 degrees.

In an embodiment, inner tips of the three legs of the circuit board arecircumferentially aligned with inner ends of the stator teeth.

In an embodiment, overmold or glue material is arranged to secure theinner tips of the three legs of the circuit board to inner teethportions of the end insulator.

According to another aspect of the disclosure, a brushlessdirect-current (BLDC) motor is provided including a rotor shaftextending along a longitudinal axis, a stator assembly, and a rotor. Thestator assembly includes a stator core, stator teeth radially extendingfrom the stator core and defining slots therebetween, stator windingswound around the stator teeth, and an end insulator mounted on an endsurface of the stator core to insulate the stator core from the statorwindings, the end insulator having a radial body and a retention postprojecting from the radial body. The rotor includes a rotor core mountedon the rotor shaft, the rotor core supporting at least one permanentmagnet that magnetically interacts with the stator windings to cause arotation of the rotor relative to the stator assembly. In an embodiment,a circuit board is mounted to the end insulator, the circuit boardincluding a front surface facing the end insulator, a rear face, and atleast one magnetic sensor mounted on the front face and configured togenerate a signal associated with an angular position of the rotor. Aretention feature is provided on a front surface of the circuit boardfacing the stator core and arranged to make a mechanical connection withthe retention post of the end insulator. In an embodiment, no portion ofretention post of the end insulator or the retention feature projectssubstantially over the rear surface of the circuit board.

In an embodiment, the circuit board includes an arcuate main body and atleast one leg projecting radially inwardly from the main body to supportat least one magnetic sensor in close proximity to the at least onepermanent magnet. In an embodiment, the at least one leg is orientedalong a radial plane that intersects the plurality of stator windings.

In an embodiment, the retention post includes a snap head and thecircuit board includes a slot arranged to receive the snap head of theretention post. In an embodiment, the snap head does not substantiallyproject out of the slot over the rear surface of the circuit board.

In an embodiment, the retention feature includes an overmold layerformed on the front surface of the circuit board facing the stator core.In an embodiment, the overmold layer forms a lip arranged at a distancefrom the front surface of the circuit board and configured to make asnap-fit connection with the snap head of the retention post.

In an embodiment, the retention feature includes a metal trap includingtwo legs mounted on the front surface of the circuit board and a mainbody distanced from the front face of the circuit board partiallyoverlapping the slot of the circuit board. In an embodiment, the mainbody is configured to make a snap-fit connection with the snap head ofthe retention post.

In an embodiment, the retention feature includes a place pad having aplanar body mounted on the front face of the circuit board, the placepad including at least one snap projecting from the planar bodyoverlapping the slot of the circuit board, the at least one snap beingresiliently flexible to make a snap-fit connection with the retentionpost.

In an embodiment, the retention post includes a recess and the retentionfeature includes a clip disposed on the front surface of the circuitboard. In an embodiment, the retention feature has an engagement edgeextending from an edge of the circuit board that is received within therecess of the retention post.

In an embodiment, a power tool is provided including a tool housing anda BLDC motor as described in any of the embodiments above.

According to another aspect of this disclosure, a power tool is providedincluding a tool housing, a support plate provided within the toolhousing, a rear tool cap separately formed from the tool housing andmounted on a rear end of the tool housing, and a brushlessdirect-current (BLDC) motor received within the housing. The BLDC motorincludes a stator assembly including a stator core having an outersurface, stator teeth radially extending from the stator core anddefining slots therebetween, and stator windings wound around the statorteeth. The BLDC motor further includes a rotor shaft extending along alongitudinal axis, a front motor bearing mounted on the rotor shaft andsupported by the support plate, a rear motor bearing mounted on therotor shaft and supported by the rear tool cap, and a rotor including arotor core mounted on the rotor shaft to rotate relative to the statorassembly. The rear end cap includes a radial body, a bearing pocketformed on or within the radial body to support the rear motor bearing, aperipheral portion that mates with the rear end of the tool housing, anda constraining member configured to engage a portion of the statorassembly to pilot the stator assembly and the rear motor bearingrelative to the rear end cap independently of the tool housing.

In an embodiment, the constraining member includes at least oneconstraining wall extending axially along a first circumference radiallyoutward of the outer surface of the stator core. In an embodiment, thefirst circumference is radially inward of the peripheral portion of therear end cap.

In an embodiment, the constraining wall includes tuning pads havinginner surfaces oriented along a second circumference that substantiallycorresponds to the outer surface of the stator core to form-fittinglyreceive the outer surface of the stator assembly within the rear endcap.

In an embodiment, the constraining wall includes two or more spacedapart arcuate constraining walls forming circumferential gapstherebetween.

In an embodiment, a motor fan is mounted on the rotor shaft within therear end cap between the stator assembly and the radial body of the rearend cap. The fan includes a main body oriented radially in line with theperipheral portion of the rear end cap and fan blades projecting towardsthe stator assembly.

In an embodiment, at least one exhaust vent is formed in the peripheralportion of the rear end cap radially aligned with the fan blades.

In an embodiment, the motor fan has a diameter that is smaller than adiameter of the outer surface of the stator core.

In an embodiment, the motor is an inner-rotor motor.

In an embodiment, the retention feature includes axial posts arranged topenetrate at least some of the stator slots in sliding contact with aportion of the stator assembly.

In an embodiment, each axial post engages an inner surface of the statorcore forming the corresponding stator slot.

In an embodiment, each axial post engages tooth tips of adjacent ones ofthe stator teeth.

In an embodiment, the axial posts traverse substantially an entirelength of the stator core.

In an embodiment, a motor fan is mounted on the rotor shaft between thestator assembly and a transmission mechanism of the power tool.

In an embodiment, the rotor core defines an annular recess within whichat portion of the rear bearing and the bearing pocket of the rear endcap are located such that the a radial plane intersects the rearbearing, the axial posts, and the rotor core.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations and are notintended to limit the scope of the present disclosure.

FIG. 1 depicts a side view of a first embodiment of a power tool, inthis example an impact tool, according to an embodiment.

FIG. 2A depicts a partial cross-sectional view of an exemplary impacttool according to an embodiment.

FIG. 2B depicts an exploded view of an impact mechanism of an exemplaryimpact tool according to an embodiment.

FIG. 3 depicts a zoomed-in partial cross-sectional view of an exemplarypower tool, according to an embodiment.

FIG. 4 depicts a side cross-sectional view of a second embodiment of apower tool including a motor assembly and support plate sized andoptimized to reduce the length of the power tool, according to anembodiment.

FIG. 5 depicts a zoomed-in side cross-sectional view of the supportplate and the motor assembly, according to an embodiment.

FIG. 6 depicts a perspective cross-sectional view of the motor assembly,according to an embodiment.

FIGS. 7A and 7B depicts perspective and side views of the motor assemblyrespectively, according to an embodiment.

FIGS. 8A and 8B depict two perspective exploded views of the same motorassembly, according to an embodiment.

FIG. 9 depict a side view of the motor assembly of FIG. 2 to illustratean advantage of the support plate and nested rotor bearingconfiguration, according to an embodiment.

FIG. 10 depicts a side view of a prior art motor without a nested rotorbearing.

FIG. 11 depicts a side cross-sectional view of the rotor, according toan embodiment.

FIG. 12 depicts a perspective exploded view of the rotor, according toan embodiment.

FIG. 13 depicts a perspective exploded view of the rotor, according toanother embodiment.

FIG. 14 depicts a perspective exploded view of the rotor, according toyet another embodiment.

FIG. 15 depicts a rear axial view of the stator assembly and the Hallboard, according to an embodiment.

FIG. 16 depicts a front axial view of the stator assembly and the Hallboard, according to an embodiment.

FIG. 17 depicts a side view of the stator assembly and the Hall board,according to an embodiment.

FIG. 18 depicts a cross-sectional side view of the stator assembly andthe Hall board from a different angle, according to an embodiment.

FIG. 19 depicts a cut-off perspective front view of the stator assemblyand the Hall board, according to an embodiment.

FIG. 20 depicts a rear perspective view of the stator assembly and theHall board, according to an embodiment.

FIG. 21 depicts a perspective view of the motor assembly including thefan and support plate, according to an embodiment.

FIG. 22 includes a rear view of the motor assembly including the fan 18,according to an embodiment.

FIG. 23 depicts a partial perspective view of the end insulatorincluding a snap post, according to an embodiment.

FIG. 24A depicts a partial perspective view of the Hall board, depictinga first embodiment of the retention feature.

FIG. 24B depicts a partial side cross-sectional view of the Hall boardwith retention feature in engagement with snap post of rear endinsulator, according to the first embodiment.

FIG. 25A depicts a partial perspective view of the Hall board, depictinga second embodiment of the retention feature.

FIG. 25B depicts a partial side cross-sectional view of the Hall boardwith retention feature in engagement with snap post of the rear endinsulator, according to the second embodiment.

FIG. 26 depicts a partial perspective view of the Hall board, depictinga third embodiment of the retention feature.

FIG. 27 depicts a perspective view of the place pad of the thirdembodiment, according to an embodiment.

FIG. 28A depicts a partial perspective view of the place pad and snappost, according to an embodiment.

FIG. 28B depicts a perspective view of the Hall board, depicting theplate pad in a bent position, according to an embodiment.

FIG. 29 depicts a partial perspective view of the end insulatorincluding a clip post, according to an embodiment.

FIG. 30 depicts a perspective frontal view of the Hall board depicting afourth embodiment of the retention feature in the form of a clip.

FIG. 31A depicts a perspective view of the Hall board secured to theclip post of the insulator via the clip, according to an embodiment.

FIG. 31B depicts a perspective view of the clip secured to the clip postof the insulator depicted without the Hall board, according to anembodiment.

FIG. 32 depicts a side view of a third embodiment of a power toolincluding an improved rear tool cap provided for interfacing with themotor assembly, according to an embodiment.

FIG. 33 depicts a perspective exploded view an improved rear tool capprovided for interfacing with the motor assembly, according to anembodiment.

FIG. 34 depicts a perspective view of the rear tool cap, according to anembodiment.

FIG. 35 depicts an axial view of the motor assembly received within therear tool cap, according to an embodiment.

FIG. 36 depicts a side cross-sectional view of the motor assemblyreceived within the rear tool cap, according to an embodiment.

FIG. 37 depicts a frontal perspective view of the motor assemblyreceived within the rear tool cap, according to an embodiment.

FIG. 38 depicts a rear perspective view of the motor assembly receivedwithin the rear tool cap, according to an embodiment.

FIG. 39 depicts a perspective view of rear tool cap, according to anembodiment.

FIG. 40 depicts an axial view of the motor assembly mounted on the reartool cap, according to an embodiment.

FIG. 41 depicts a side cross-sectional view of the motor assemblymounted on the rear tool cap, according to an embodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings. It is to be understood that both theforegoing general description and the following detailed description areexemplary and explanatory only and are intended to provide anexplanation of various embodiments of the present teachings.

FIG. 1 depicts a side view of a power tool 10, in this example an impacttool, according to an embodiment. FIG. 2A depicts a partialcross-sectional view of the exemplary impact tool 10 according to anembodiment. FIG. 2B depicts an exploded view of the exemplary impacttool 10 according to an embodiment. FIG. 3 depicts a zoomed-in partialcross-sectional view of the exemplary power tool 10, according to anembodiment.

In an embodiment, the exemplary impact tool 10 includes a housing 12having a motor housing portion 23 including two clamshells that cometogether to house a motor 100 rotatably driving a rotor shaft 102 and atransmission housing portion 21 coupled to the motor housing portion 23that houses a transmission assembly 20 and an impact mechanism 40 thattogether selectively impart rotary motion and/or a rotary impact motionto an output spindle 26. Coupled to the output spindle 26 is a toolholder 28 for retaining a tool bit (e.g., a drill bit, a screw drivingbit, or a socket wrench, not shown). Further details regarding exemplarytool holders are set forth in U.S. patent application Ser. No.12/394,426, which is incorporated herein by reference. The power toolfurther includes a handle 13 that extends transverse to the housing 12and accommodates a trigger switch 15, a control and/or power module (notshown) that includes control electronics and switching components fordriving the motor 100, and a battery receptacle 17 that receives aremoveable power tool battery pack for supplying electric power to themotor 100. The handle 13 has a proximal portion coupled to the housing12 and a distal portion coupled to the battery receptacle 17. The motor100 may be powered by an electrical power source, such as a DC powersource or battery (not shown), that is coupled to the battery receptacle17, or by an AC power source. The trigger 15 is coupled to the handle 13adjacent the housing 12. The trigger 15 connects the electrical powersource to the motor 100 via the control and/or power module, whichcontrols power delivery to the motor 100.

In an embodiment, the transmission assembly 20 may comprise a planetarytransmission and may include, among other features, a pinion or sun gear24 that is coupled to an end of the rotor shaft 102 of the motor 100 andthat extends along a tool axis X. One or more planet gears 48 surroundand have teeth that mesh with the teeth on the sun gear 24. An outerring gear 30 is rotationally fixed to the housing 12 and centered on thetool axis X with internal teeth meshing with the teeth on the planetgears 48. A cam carrier 22 includes a pair of carrier plates 22A, 22Bthat support the planet gears 48 with pins 55 so that the planet gears48 can rotate about the pins 55. The cam carrier 52 further includes arearward protrusion 57 that extends axially rearward from the rearcarrier plate 22A along the axis X and a cam shaft 59 that extendsaxially forward from the front carrier plate 22B along the axis X.

When the motor 100 is energized, the rotor shaft 102 and the sun gear 24rotate about the axis X. Rotation of the sun gear 24 causes the planetgears 48 to orbit the sun gear 24 about the axis X, which in turn causesthe cam carrier 22 to rotate about the axis X at a reduced speedrelative to the rotational speed of the rotor shaft 102. In theillustrated embodiment, only a single planetary stage is shown. Itshould be understood that the transmission may include multipleplanetary stages that may provide for multiple speed reductions, andthat each stage can be selectively actuated to provide for multipledifferent output speeds of the planet carrier. Further, the transmissionmay include a different type of gear system such as a parallel axistransmission or a spur gear transmission.

The impact mechanism 40 includes the cam shaft 59, a generallycylindrical hammer 42 received over the cam shaft 59, and an anvil 44fixedly coupled to the output spindle 26. The hammer 42 has two lugs 45configured to engage two radial projections 46 on the anvil 44 in arotating direction. Formed on an outer surface of the cam shaft 59 is apair of rear-facing V-shaped cam grooves 47 with their open ends facingtoward transmission assembly 20. A corresponding pair of forward-facingV-shaped cam grooves (not shown) is formed on an interior surface of thehammer 42 with their open ends facing toward the output spindle 26.Balls 49 are received in and rides along each of the cam grooves 47 tomovably couple the hammer 42 to the cam shaft 59. A compression spring41 is received in a cylindrical recess in the hammer 42 and abuts aforward face of the front carrier plate 22B. The spring 41 biases thehammer 42 toward the anvil 44 so that the so hammer lugs 45 engage thecorresponding anvil projections 44.

At low torque levels, the impact mechanism 40 transmits torque from thetransmission assembly 20 to the output spindle 26 in a rotary mode. Inthe rotary mode, the compression spring 41 maintains the hammer 42 in aforward position so that the hammer lugs 45 continuously engage theanvil projections 46. This causes the cam shaft 59, the hammer 42, theanvil 44, and the output spindle 26 to rotate together as a unit aboutthe axis X. As torque increases, the impact mechanism 40 may transitionto transmitting torque to the output spindle 26 in an impact mode. Inthe impact mode, the hammer 44 moves axially rearwardly against theforce of the spring 41, decoupling the hammer lugs 45 from the anvilprojections 46. The anvil 44 continues to spin freely on about the axisX without being driven by the motor assembly 100 and the transmissionassembly 20, so that the anvil 44 coasts to a slower speed. Meanwhile,the hammer 42 continues to be driven at a higher speed by the motorassembly 100 and transmission assembly 20, while the hammer 42 movesaxially rearwardly relative to the anvil 44 by the movement of the balls49 in the V-shaped cam grooves 47. When the balls 49 reach theirrearmost position in the V-shaped cam grooves 47, the spring 41 drivesthe hammer 42 axially forward with a rotational speed that exceeds therotational speed of the anvil 44. This causes the hammer lugs 45 torotationally strike the anvil projections 46, imparting a rotationalimpact to the output spindle 26.

In an embodiment, the motor 100 is a brushless direct-current (BLDC)motor that includes an inner rotor 104 having surface-mount magnets 106on a rotor core 108 and a stator assembly 110 located around the rotor104. The stator assembly 110 includes a stator core 112 having a seriesof teeth 114 projecting radially inwardly from the stator core 112, anda series of conductive windings 113 wound around the stator teeth 114 todefine three phases connected in a wye or a delta configuration. As thephases of the stator assembly 110 are sequentially energized, theyinteract with the rotor magnets 106 to cause rotation of the rotor 104relative to the stator assembly 110.

In an embodiment, the rotor core 108 is mounted on the rotor shaft 102and includes an annular recess 116 around the rotor shaft 102 on oneside of the rotor core 104. Specifically, the rotor 104 is provided withwhat is referred to in this disclosure as an open-core construction,where the rotor magnet 106 is mounted around the rotor core 112 and theannular recess 116 is provided within the rotor core 112 for positioningof one or more of the rotor bearings. The rotor core 112 may be made ofa solid core piece of metal or lamination stack that includes a seriesof parallel laminations. The annular recess 116 may be carved or stampedout of the rotor core 112, or it may be formed using ring-shapedlaminations.

In an embodiment, the rotor magnet 106 is a ring surface-mounted on theouter surface of the rotor core 108 and magnetized in a series of poles,e.g., four poles having a S-N-S-N orientation. Alternatively, rotormagnet 106 may be provided as a series of discrete magnet segments thatmay be pre-magnetized prior to assembly. The outer surface of the rotorcore 108 may be shaped for proper retention of the magnet segments. Inyet another embodiment, the rotor magnets 106 may be fully or partiallyembedded within the rotor core 108.

In an embodiment, a fan 118 is mounted on the rotor shaft 102 behind themotor assembly 100. In an embodiment, a rear tool cap 14 is mounted tothe end of the housing 12 to contain the end of the motor 100. The reartool cap 14 may be provided integrally with the housing 12 or as aseparate piece. In an embodiment, the fan 118 is positioned between themotor 100 and the rear tool cap 14. The fan 118 generates airflowthrough the motor 100 and (preferably) the transmission assembly 20 tocool the components.

In an embodiment, a support plate 130 supports front and rear motorbearings 158 and 160 that support the rotor shaft 102. At least the rearmotor bearing 160 is located within the stator assembly 110 and withinthe annular recess 116 of the rotor core 108 along the axial directionof the motor 100 such that the rear motor bearing 160 intersects aportion of the rotor core 108 along a radial plane. The support plate130 includes a cylindrical portion 132 that receives the outer races ofthe motor bearings 158 and 160 and a radial portion 134 that extendsradially from the cylindrical portion 132 and includes radial endssupported by the tool housing 12. The stator assembly 110 is alsosupported by the tool housing 12, thus being axially and radially securewith respect to the support plate 130. In this manner, the support plate130 axially and radially supports the rotor 104 within the statorassembly 110. In an embodiment, the support plate 130 and the statorassembly 110 may be independently supported by the tool housing 12. Inanother embodiment, the support plate may be formed integrally as a partof two clamshells that form the tool housing 12. Alternatively, thesupport plate 130 may be piloted to and retained by the stator assembly110 directly and independently of the tool housing 12.

In an embodiment, as shown in FIGS. 2A and 3, the support plate 130 alsohas a front lip 131 that supports a component of the transmissionassembly 20, such as supporting the ring gear 30, to inhibit axially androtational movement of the ring gear 30 relative to the housing 12. Inaddition, the support plate 130 supports a cam carrier bearing 32 thatsupports the cam carrier 22 relative to the support plate 130, andtherefore relative to the motor 100 and the tool housing 12. The camcarrier bearing 32 is nested within the support plate 130 adjacent themotor 100. Specifically, the support plate 130 is positioned between themotor assembly 100 and transmission assembly 20 and provides support forthe motor bearings 158 and 160 on one side and for the cam carrierbearing 32 on the other side. In an embodiment, the support plate 130includes a recessed portion 136 that includes a larger diameter than thecylindrical portion 134 and is sized to receive the cam carrier bearing32 therein. The cam carrier bearing 32 is thus located axially forwardof the entire motor assembly 100.

At least a portion of the support plate 130 is received within thestator assembly 110 and within the rotor core 108. In this embodiment,the rear cylindrical projection of the support plate that supports themotor bearings 158 and 160 is at least partially received within thestator assembly 110 and within the motor core 108. In this embodiment,the nested arrangement of the one or more motor bearings 158 and 160 andthe support plate 130 provide a compact motor assembly 100 compared toconventionally available brushless motors. Disposition of the one ormore bearings 158 and 160 and at least a portion of the support plate130 within the stator assembly 110 and within the rotor core 108 reducesthe length of the motor assembly 100 and the overall power tool andimproves power density.

In an embodiment, motor assembly 100 defines a motor envelope 120bounded by a rear plane 122 at a rearmost point of the motor assembly100 (i.e., at the rearmost point of the stator assembly 110), a frontplane 124 at a frontmost point of the motor assembly 100 (i.e., at thefrontmost point of the stator assembly 110), and a generally cylindricalboundary 126 extending from the rear plane 122 to the front plane 124and surrounding a radially outermost portion of the motor assembly 100(e.g., a radially outermost portion of the stator assembly 110) notincluding terminal block 121. In the illustrated embodiment, the rearplane 122 is at a rearmost point of the stator assembly 110 (includingits windings 113), the front plane 124 is at a frontmost point of thestator assembly 110 (including its windings 113), and the generallycylindrical boundary 126 surrounds a radially outermost portion of thestator assembly 110. However, it should be understood that the rearplane may be at a rearmost point of the rotor 104 (if that extendsfurther rearward than the stator assembly 110), the front plane may beat a frontmost point of the rotor 104 (if that extends further frontwardthan the stator assembly 110), and the generally cylindrical boundarymay be at an outermost point of the rotor 104 (if that extends furtherradially outward than the stator assembly 110, e.g., in an outer rotormotor). The motor envelope 120 may have a length L1 from the rear plane122 to the front plane 124 of approximately 16 mm to 20 mm (e.g.,approximately 18.4 mm) and a diameter D1 of the cylindrical boundary 126of approximately 40 mm to 60 mm (e.g., approximately 51 mm), with avolume of approximately 20 cm² to 56 cm² (e.g., approximately 38 cm²).In an embodiment, at least a portion of at least one of the motorbearings 158 and 160 and at least a portion of the support plate 130 arereceived within the motor envelope 120.

An alternative embodiment of a power tool 50 is described herein withreference to FIGS. 4-10. FIG. 4 depicts a side cross-sectional view ofthe power tool 50 including a motor assembly 200 and support plate 230sized and optimized to reduce the length of the power tool 50, accordingto an embodiment. In an embodiment, power tool 50 includes many of thesame features as power tool 10 described above, such as transmissionassembly 20, impact mechanism 40, output spindle 26, tool holder 28,handle 13, trigger 15, battery receptacle 17, etc., details of which arenot repeated here, except as necessary to describe this alternativeembodiment. In an embodiment, a rear end cap 50 is mounted on a rear endof the housing 52 rearward of the motor assembly 200. In thisembodiment, the support plate 130 is designed to locate the cam carrierbearing 32 along the same radial plane as at least an end of the statorwindings, so the cam carrier bearing 32 is located at least partiallywithin an envelope formed by the ends of the motor assembly 200.

In an embodiment, motor assembly 200 includes many of the same featuresdescribed above with reference to FIG. 1. In an embodiment, motorassembly 200 includes a rotor shaft 202, an inner rotor 204 mounted onthe rotor shaft 202 having a surface-mount magnet ring 206 on a rotorcore 208, and a stator assembly 210 located around the rotor 204. Thestator assembly 210 includes a stator core 212, a series of stator teeth214 radially projecting inwardly from the stator core 212, and a seriesof conductive windings 113 wound around the stator teeth 214 to definethree phases connected in a wye or a delta configuration.

In an embodiment, the motor assembly 200 defines a tool axis X extendingthrough the center of the rotor shaft 202 extending from a rear of thepower tool 50 (i.e., where the rear end cap 50 is located) to a front ofthe power tool (i.e., where tool holder 28 is located). In thisdisclosure, the terms “rear” and “front” are used to describe positionsof various components along the tool axis X in the direction A shown inFIG. 4. Thus, as an example, the motor assembly 200 is disposedrearwardly of the transmission assembly 20.

In an embodiment, the rotor core 208 is mounted on the rotor shaft 202and includes an annular recess 216 around the rotor shaft 202 on oneside of the rotor core 208 for positioning of one or more of the rotorbearings 258 and 260. The rotor core 212 may be made of a solid corepiece of metal or lamination stack that includes a series of parallellaminations. The annular recess 216 may be carved or stamped out of therotor core 212, or it may be formed using ring-shaped laminations. Therotor magnet 106 may be ring-sized or segmented, and it may besurface-mounted or embedded within the rotor core 208.

FIG. 5 depicts a zoomed-in side cross-sectional view of the supportplate 230 and the motor assembly 200, according to an embodiment. FIG. 6depicts a perspective cross-sectional view of the motor assembly 200,according to an embodiment. FIGS. 7A and 7B depicts perspective and sideviews of the motor assembly 200 respectively, according to anembodiment. FIGS. 8A and 8B depict two perspective exploded views of thesame motor assembly 200, according to an embodiment. Various aspects ofthe motor assembly 200 ant the support plate 230 are described withreference to these figures.

In an embodiment, the support plate 230 includes a first bearing pocket232 formed as a cylindrical or rim-shaped projection from a radialportion 234 for supporting at least the front motor bearing 258. Thefirst bearing pocket 232 of the support plate 230 at least partiallyprojects into and is received within the annular recess 216 of the rotor204. This allows the front bear motor bearing 258 to be received atleast partially within the stator assembly 210 and within an envelope ofthe rotor core 208 defined by the radial surfaces of the rotor core 208.

In an embodiment, the support plate 230 further includes a secondbearing pocket 236 for supporting the cam carrier bearing 32. The secondbearing pocket 236 may be formed as a recessed portion of the radialportion 234 of the support plate 230 facing away from the first bearingpocket 232. In an embodiment, second bearing pocket 236 is formed as anintermediate annular portion formed between the radial portion 234 and aradial wall 235, where the radial portion 234 is located along a radialplane that intersects a portion of the stator assembly 210, and theradial wall 235 is located adjacent a front end of the stator assembly210. As such, the radial portion 234 extends between a front end of thefirst bearing pocket 232 and a rear end of the second bearing pocket236. In an embodiment, the radial wall 235 extends from the front end ofthe second bearing pocket 236 radially outwardly and is supported byeither the tool housing 52 or the stator assembly 210. In an embodiment,support plate 230 further includes an outer rim portion or lip 237projecting axially forward from an outer circumference of the radialwall 235 for coupling with an outer portion of the transmission housing21 and/or the tool housing 52 and for receiving and supporting acomponent of the transmission assembly 20, such as the ring gear 30 ofthe transmission assembly 20.

In an embodiment, the second bearing pocket 236 has a larger innerdiameter than the first bearing pocket 232. In an embodiment, secondbearing pocket 236 has approximately the same inner diameter as theoutside surface of the rotor core 208. In an embodiment, the outersurface of the second bearing pocket 236 is received within the openingof the stator 210, i.e., within the inner diameter formed by front endsof the stator windings 224 adjacent the rotor 204. In an embodiment, theouter annular surface of the second bearing pocket 236 may be inphysical contact with the stator windings 224 or a front end insulator220 of the stator assembly 210, though in the illustrated figured, asmall air gap 217 radially separates the outer annular surface of thesecond bearing pocket 236 from the stator windings 224 and the front endinsulator 220 of the stator assembly 210.

In an embodiment, the cam carrier bearing 32 is received within thesecond bearing pocket 236 so that it is at least partially nested withinthe stator assembly 210 along a radial plane A′ that intersects thefront ends of the stator windings 224.

In an embodiment, the motor assembly 200 defines a motor envelope 240similar to the motor envelope 120 of the motor 100, described above. Themotor envelope 240 is bounded by a rear plane 242 at a rearmost point ofthe motor assembly 200 (i.e., at the rearmost point of the statorassembly 210), a front plane 244 at a frontmost point of the motorassembly 200, and a generally cylindrical boundary 246 extending fromthe rear plane 242 to the front plane 244 and surrounding a radiallyoutermost portion of the motor assembly 200 (e.g., a radially outermostportion of the stator assembly 210). In the illustrated embodiment, therear plane 242 is at a rearmost point of the stator assembly 210(including its stator windings 224), the front plane 244 is at afrontmost point of the stator assembly 210 (including its statorwindings 224), and the generally cylindrical boundary 246 surrounds aradially outermost portion of the stator assembly 210 (not including theterminal block 221). However, it should be understood that the rearplane may be at a rearmost point of the rotor 204 (if that extendsfurther rearward than the stator assembly 210), the front plane may beat a frontmost point of the rotor 204 (if that extends further frontwardthan the stator assembly 210), and the generally cylindrical boundarymay be at an outermost point of the rotor 204 (if that extends furtherradially outward than the stator assembly 210, e.g., in an outer rotormotor). As shown in FIGS. 4 and 5, the motor envelope 240 may have alength L3 from the rear plane 242 to the front plane 244 ofapproximately 16 mm to 20 mm (e.g., approximately 18.4 mm) and adiameter D1 of the cylindrical boundary 246 of approximately 40 mm to 60mm (e.g., approximately 51 mm), with a volume of approximately 20 cm² to56 cm² (e.g., approximately 38 cm²). In an embodiment, at least aportion of the front motor bearing 258 and at least a portion of thesupport plate 230 are received within the motor envelope 120.

In an embodiment, as best seen in FIGS. 8A and 8B, support plate 230 isprovided with radially outwardly extending axial posts or fins 238provided for piloting and supporting the support plate 230 relative tothe stator assembly 210. In an embodiment, axial posts 238 are receivedwithin respective slots of the stator assembly 210 formedcircumferentially between stator windings 224. In an embodiment, axialposts 238 come into contact with the inner surface of the stator core212 or adjacent inner tips of the stator teeth 214. In this manner, thesupport plate 230 is radially supported with respect to the statorassembly 210 independently of the power tool housing 52. In anembodiment, support plate 230 further includes one or morecircumferential projections 239 that engage a portion of the toolhousing 52 to provide axial support for the support plate 230 relativeto the stator assembly 210. In an embodiment, a series of six axialposts 238 are provided, each project from a rear surface of the radialwall 235 around the first bearing pocket 232. In an embodiment, lengthof the axial posts 238 is approximately equal to or greater than thelength of the first bearing pocket 232 in the direction of the statorassembly 210 to allow the axial posts 238 to extend into the slots ofthe stator assembly 210. Reference is made to US Patent Publication No.2017/0294819A1, which is incorporated herein by reference in itsentirety, for a description of the axial posts for piloting and supportof a bearing support structure relative to the inner diameter of thestator.

In an alternative embodiment not shown here, instead of axial posts 238,the support plate 230 may be piloted and supported via one or morecircumferential constraining walls that extend over the outside surfaceof the stator core 212. Reference is made to U.S. Pat. No. 10,056,806,which is incorporated herein by reference in its entirety, for adescription of the peripheral walls for piloting and support of abearing support structure relative to the outer diameter of the stator.

In an embodiment, stator assembly 210 includes front and rear endinsulators 220 and 222 disposed on axial ends of the stator core 212 toelectrically insulate the stator windings 224 from the stator core 212.In an embodiment, one or more of the end insulators 220 and 222 supporta terminal block 221 on the lower surface of the stator core 212. Theterminal block 221 includes a series of motor terminals that connect viaa series of wires to a power module (not shown) disposed in the toolhousing 52 to receive electric power. The motor terminals are alsoelectrically connected to the stator windings 224. In an embodiment, theterminal block 221 is provided along a radial plane A″ that alsointersects the front motor bearing 258 and the rotor magnet ring 206.

In an embodiment, both motor bearings 258 and 260 may be supported atleast partially within the rotor annular recess 216 if the length of thestator core 212 and the corresponding length of the rotor core 208 issufficiently large to accommodate both motor bearings 258 and 260.Alternatively, in an embodiment as shown in FIG. 2, where the length ofthe rotor core 208 is not sufficiently large to receive both bearings258 and 260 within the annular recess 216, the front motor bearing 258is supported within the annular recess 216 of the rotor core 212 whilethe rear motor bearing 260 is supported in rear tool cap 54 of the toolhousing 52. In an embodiment, rear tool cap 54 includes a radial bodythat includes a central bearing pocket 56 for supporting the rear motorbearing 260. In an embodiment, rear tool cap 54 includes a peripheralportion 58 that is secured to the tool housing 52. Alternatively, therear tool cap 54 may be formed integrally as a part of the clamshellthat forms the tool housing 52.

In an embodiment, fan 218 is mounted on the rotor shaft 202 to rotatewith the rotation of the motor 200. The fan 218 includes a radial mainbody and a plurality of blades facing the stator assembly 210. In anembodiment, an inner portion of the fan 218 is recessed to allow therear motor bearing 260 to be nested at least partially in the axialdirected within the fan 218 to be aligned radially with the main body ofthe fan 218. The central bearing pocket 56 of the rear tool cap 54 isaxially received within the recess portion of the fan 218 around therear motor bearing 260. In this manner, positioning of the rear motorbearing 260 within the rear tool cap 54 does not pose a significantincrease in the overall length of the motor assembly 200.

FIG. 9 depict a side view of the motor assembly 200 of FIG. 2 toillustrate an advantage of the support plate configuration describedabove, where the front motor bearing 258 is nested within the envelopeof the stator assembly 210 and at least partially within the rotor 204.In the event of egregious movement of the rotor shaft 202 due to a fall,high vibration, or high impact, the rotor shaft 202 may be pivoted awayfrom the longitudinal axis relative to the stator assembly 210. Thispivoting movement may take place around a pivot point 262 aligned withthe front motor bearing 258. The pivot point 262 is associated withtolerances in the bearings of the front motor bearing 258, tolerancesbetween the front motor bearing 258 and the rotor 204, and/or tolerancesbetween the front motor bearing 258 and the stator assembly 210. Sincethe pivot point 262 is located within the envelope of the statorassembly 210, in the event of such a pivoting movement of the rotorshaft 202, the likelihood that the rotor shaft 202 makes physicalcontact with the stator assembly 210 is significantly reduced.

By comparison, FIG. 10 depicts a side view of a prior art motor 300, inwhich the front rotor bearing 358 is not nested within the rotor 304 andtherefore provided outside the envelope of the stator assembly 310. Inan embodiment, in the event of egregious rotor shaft movement, the pivotpoint 362 for pivoting movement of the rotor shaft 302 relative to thelongitudinal axis is located away from the stator assembly 310. Thus, inthe event of a pivoting movement of the rotor shaft 302, there is alikelihood that the rotor shaft 302 makes physical contact with aportion of the stator assembly 310.

Various embodiments of the rotor 204 including the outer magnet ring 206are described here with reference to FIGS. 11-14.

FIG. 11 depicts a side cross-sectional view of the rotor 204, accordingto an embodiment. FIG. 12 depicts a perspective exploded view of therotor 204, according to an embodiment. In an embodiment, as describedbriefly previously, the rotor 204 includes a permanent magnet ring 206that is sized to be received over an outside surface of the rotor core208. The magnet ring 206 may be made of sintered, hot-extrusion (MQ3),bonded, and/or injection-molded magnetic material. In anotherembodiment, the magnet ring 206 comprises a sintered magnet includingmagnet alloy that is pulverized, magnetically aligned within a magneticfield for magnetization, press molded, and then sintered. In anembodiment, magnet ring 206 may comprise a series of discrete permanentmagnets mounted on the rotor core 208 as a unit. In an embodiment, thediscrete magnets may be bonded together before or after magnetization.In an embodiment, the rotor core 208 may include a fully annular body.

In an embodiment, to properly secure the magnet ring 206, a thin layerof adhesive is provided between the magnet ring 206 and the rotor core208. To accommodate the adhesive, in an embodiment, the inner diameterof the magnet ring 206 in this case is slightly greater than the outerdiameter of the rotor core 208. This may cause the magnet ring 206 to beacentric relative to the rotor core 208.

Alternatively, in an embodiment, as shown in FIGS. 11 and 12, the rotorcore 208 includes two annular alignment rings 280 at its two axial ends.Annular alignment rings 280 may be provided by carving out a middle area282 of the rotor core 208 such that each of the annular alignment rings280 have a slightly greater diameter than the middle area 282, e.g., byapproximately 0.1 mm to 0.6 mm, preferably 0.1 mm to 0.3 mm. Theadhesive (not shown) is applied on the middle area 282 of the outersurface of the rotor core 208 for retaining the magnet ring 206. Annularalignment rings 280 have approximately the same diameter as the innerdiameter of the magnet ring 206 to ensure a tight fit and properalignment between the magnet ring 206 and the rotor core 208.

FIG. 13 depicts a perspective exploded view of the rotor 204, accordingto another embodiment. In this embodiment, rotor core 208 includes aseries of alignment rings 290, forming annular grooves 292 therebetween.Annular grooves 292 may be, for example, 0.05 to 0.3 mm deep relative tothe outer surface of the rotor core 208. The adhesive (not shown) isapplied within the grooves 292 for retaining the magnet ring 206.Annular alignment rings 290 have approximately the same diameter as theinner diameter of the magnet ring 206 to ensure a tight fit and properalignment between the magnet ring 206 and the rotor core 208.Alternatively, in an embodiment, annular alignment rings 290 has aslightly smaller diameter than the inner diameter of the magnet ring 206to allow the adhesive to spread over the outer surface of rotor core208, though this arrangement may require an additional equipment forproper alignment of the rotor core 208 and the magnet ring 206.

FIG. 14 depicts a perspective exploded view of the rotor 204, accordingto yet another embodiment. In this embodiment, rotor core 208 includes aseries of axial pads 296 along its outer surface. Axial pads 296 projectfrom the outer surface of the rotor core 208 by approximately 0.05 mm to0.3 mm, forming a series of axial channels 298 in between. The adhesive(not shown) is applied within the axial channels 298 on the outersurface of the rotor core 208 for retaining the magnet ring 206. Theinner diameter of the magnet ring 206 is sized to be form-fittinglyreceived in contact with the axial pads 296 to ensure a tight fit andproper alignment between the magnet ring 206 and the rotor core 208.

Referring back to FIGS. 7 and 8, motor assembly 200 includes a circuitboard (hereinafter referred to as Hall board) 400 is mounted on thestator assembly 210. Hall board 400 includes a series of magnetic (Hall)sensors arranged to sense a magnetic flux of the magnet ring 206. Aseries of signal wires 402 are coupled to a first connector 404 that ismounted on the Hall board 400 on one end and a second connector 406 thatis coupled to the controller (not shown) on the other end. The signalwires 402 provide signals related to an angular position of the rotor204 to the controller.

Use of Hall boards for detection of the angular position of the rotor iswell known. Hall boards provide signals related to the magnetic positionof the rotor to a controller, which uses the information for calculatingthe timing of commutation of the next phase of the motor.Conventionally, a Hall board is rectangular shaped with three Hallsensors positioned at predetermined angular positions to sense the rotorrotary position. Also, conventionally, a sense magnet ring is providedin addition to the rotor magnet and mounted on the rotor shaft adjacentthe rotor lamination stack. The Hall sensors are axially aligned withthe sense magnet ring, and the sense magnet ring has an axial magneticflux that is sensed by the hall sensors. Disposition of the hall boardadjacent the stator, and addition of the sense magnet ring, add tooverall motor length and cost of manufacturing.

Hall board 400 is described herein in detail with reference to FIGS.15-22, according to an embodiment. In an embodiment, as described herein detail, no sense magnet ring is provided, and the Hall board 400 isdesigned to directly sense the leakage flux of the rotor magnet ring206. In addition, the Hall board 400 is designed to add little or nolength to the motor assembly 200. Various embodiments for coupling thehall board 400 to the stator assembly 210 are described in detail withreference to FIGS. 23-32.

FIGS. 15 and 16 depict rear and front axial views of the stator assembly210 and the Hall board 400, according to another embodiment. FIG. 17depicts a side view of the stator assembly 210 and the Hall board 400,according to another embodiment. FIG. 18 depicts a cross-sectional sideview of the stator assembly 210 and the Hall board 400 from a differentangle, according to another embodiment. FIG. 19 depicts a cut-offperspective front view of the stator assembly 210 and the Hall board400, according to another embodiment. FIG. 20 depicts a rear perspectiveview of the stator assembly 210 and the Hall board 400, according toanother embodiment.

As shown in these figures, in an embodiment, the Hall board 400 includesa main body 410 that is arcuate shaped and overlays the rear surface ofthe end insulator 222 of the stator assembly 210, three legs 412 a, 412b, 412 c that extend radially inwardly from the main body 410. The legs412 a-c penetrate the stator slots formed between the ends of the statorwindings 224 substantially radially in-line with the ends of the statorwindings 224. In an embodiment, the main body 410 covers approximatelyan angular range ‘θ’ of the stator assembly 210, where θ is in the rangeof 120-140 degrees, preferably approximately 125-135 degrees, morepreferably approximately 130 degrees.

In an embodiment, main body 410 of the Hall board 400 has a curvaturethat generally corresponds to the curvature of the stator assembly 210.In an embodiment, main body 410 is shaped such that, when viewed alongthe axis direction of the motor assembly 200, a first portion 414 of themain body 410 does not substantially extend beyond the periphery of theouter surface of the stator core 212. In an embodiment, first portion414 covers an angular distance 81 in the range of approximately 35 to 55degrees, preferably approximately 40 to 50 degrees. In an embodiment,while a lip 411 of the first portion 414 along the leg 412 a slightlyprotrudes beyond the periphery of the outer surface of the stator core212, the remainder of the first portion 414 is substantially containedwithin a peripheral envelope of the stator core 212.

In an embodiment, a second portion 416 of the peripheral surface of themain body 410, however, does extend beyond the periphery of the outersurface of the stator core 212 to provide a mounting area for the firstconnector 404 and receiving through-holes for fasteners 420. In anembodiment, the second portion 416 covers an angular distance 82 in therange of approximately 60 to 90 degrees, preferably approximately 70 to80 degrees. In an embodiment, the second portion 416 radially intersectslegs 412 b and 412 c.

In an embodiment, the two fasteners 420 are received throughcorresponding through-holes of the Hall board 400 and the rear endinsulator 222 and received into threaded receptacles of the front endinsulator 220 in order to secure the Hall board 400 is secured to thestator assembly 210.

In an embodiment, front and rear end insulators 220 and 222 togetherform a mounting support structure 430 that project radially outwardlyfrom the stator assembly 210 and securely supports the terminal block221 on the outer surface of the stator core 212. In an embodiment, thethrough holes of the end insulator 222 and threaded receptacles of thefront end insulator 220 are provided on the mounting support structure430. In an embodiment, the terminal block 221 is thus provided adjacentthe first connector 404 of the Hall board 400.

In an embodiment, terminal block 221 includes a series of three motorterminals 432 provided parallel to the longitudinal axis of the motorand mounted on an insulating mount 434. Each of the motor terminals 432includes a folded tang portion 436 around which the magnet wires of thecorresponding stator windings 224 are wrapped and fused, and a tabportion 438 to which the corresponding power wires are coupled. U.S.Pat. No. 9,819,241, which is incorporated herein by reference in itsentirety, provides a full description of terminal block 221. In anembodiment, second portion 416 of the main body 410 has a periphery thatextends in line with the insulating mount 434 so as to position thefirst connector 404 substantially in line with the tab portions 438 ofthe motor terminals 432.

In an embodiment, second portion 416 of the Hall board 400, togetherwith the terminal block 221, may be received partially within the handle13 of the power tool below the motor housing portion 23. The orientationof the first portion 414 of the Hall board 400 within thecircumferential envelope of the stator core 212 ensures that the Hallboard 400 does not increase the overall girth of the motor assembly 200within the motor housing portion 23.

In an embodiment, legs 412 a-c of the Hall board 400 penetrate inbetween the ends of the stator windings 224 and the main body 410 ismounted in contact with the end insulator 222. As best shown in the sideviews of FIGS. 17 and 18, this arrangement allows the Hall board 400 tobe positioned in the radial position approximately within motor envelope240 (see FIG. 5), with legs 412 a-412 c being contained fully within themotor envelope 240. Motor envelope 240 in this embodiment is bound byrear plane 242 at a rearmost point of the stator windings 224, frontplane 244 at a frontmost point of the stator windings 224, and generallycylindrical boundary 246 surrounding the radially outermost portion ofthe stator assembly 210 not including the terminal block 211. In anembodiment, at least a portion of the Hall board 400 opposite the statorcore 212 is positioned along approximately the rear plane 242, whichintersects the rear ends of the stator windings 224. In an embodiment,the rear surface of the Hall board 400 opposite the stator core 212 ispositioned along approximately the rear plane 242.

This arrangement eliminates or substantially reduces any contribution bythe Hall board 400 to the overall size and length of the motor assembly200. In compact motor applications such as cordless power tools, wheresignificant research and development is dedicated to optimizing thepower density of the motor, a reduction is length of even a fewmillimeters is significant.

In an embodiment, mounted on the front surface of the Hall board 400facing the rotor 204 are a series of three Hall sensors 450 disposednear the inner ends 452 of the three legs 412 a-c. In an embodiment, theHall sensors 450 are positioned circumferentially in-line with innerends of the stator teeth 214 or inner ends of the stator windings 224when viewed along the axis direction, as best seen in FIGS. 15, 16, 19and 20. In an embodiment, the inner ends 452 of the legs 412 a-c arecircumferentially in-line with inner ends 215 of the stator teeth 214and Hall sensors 450 are circumferentially in-line with inner portions225 of the stator windings 224. This arrangement positions the Hallsensors 450 sufficiently close to the rotor magnet ring 206 for directsensing of the rotor magnet ring 206 without a need for an additionalsense manet, thus further reducing the axial length of the motorassembly 200.

In an embodiment, an overmold or glue material 460 on two sides of thelegs 412 a-c of the Hall board 400 near the inner ends 452 to secure thelegs 412 a-c to teeth portions 462 of the end insulator 222 of thestator assembly 210. This ensures that the legs 412 a-c of the Hallboard 400 are protected against damage due to vibration.

FIG. 21 depicts a perspective view of the motor assembly 200 includingthe fan 218 and support plate 230, according to an embodiment. FIG. 22includes a rear view of the motor assembly 200 including the fan 218,according to an embodiment.

In an embodiment, connector 404 and fasteners 420 are provided on thesecond portion 416 of the Hall board 400, outside the peripheral area ofthe motor fan 218. Heads of the fasteners 420, which may have athickness of 1 mm or more, and the connector 404, are elementsassociated with Hall board 400 that project slightly rearwardly of theHall board 400 in the axial direction. However, since the connector 404and fasteners 420 are positioned outside the peripheral area of themotor fan 218, the motor fan 218 may be positioned in close axialproximity to the Hall board 400, with fan blades 470 rotatablypositioned in very close proximity to the rear surface of the Hall board400. In an embodiment, the distance between the fan blades 470 and theHall board 400 is approximately 1.5 mm or less. This allows the Hallboard 400 to be secured to the stator assembly 210 without increasingthe relative distance between the motor fan 218 and the stator assembly210.

Referring back to FIGS. 15 and 20, while fasteners 420 sufficientlysecure legs 412 b and 412 c of the Hall board 400 relative to the statorassembly 210, leg 412 a is provided at a distance from both fasteners420 and is therefore prone to movement and breakage due to highvibration without an additional retention feature in its vicinity. Toovercome this, in an embodiment, a slot 472 is provided on the main body410 of the Hall board 400 radially outwardly of the leg 412 a thatreceives a snap post 482 of the rear end insulator 222. Moreover, aretention feature 480 is provided to mechanically secure the snap post482 of the rear end insulator 222 to the Hall board 400 proximate theslot 472. In an embodiment, retention feature 480 is designed to allow asnap connection or sliding connection between the Hall board 400 and thesnap post 482 of the rear end insulator 222, without adding the lengthof the motor assembly 200. In an embodiment, retention feature 480 maybe made as a detachable or inseparable snap-fit connection.

FIG. 23 depicts a partial perspective view of the rear end insulator222, according to an embodiment. In an embodiment, snap post 482 of therear end insulator 222 that extends along the longitudinal axis of themotor assembly 200. In an embodiment, snap post 482 includes a snap head483 that is received within the slot 472 of the Hall sensor as the Hallboard 400 is being mounted on the end insulator 222, an entrance side484 for sliding engagement with the retention feature 480 as the snaphead 483 is being received within the slot 472, and an undercut portion486 that makes a snap-fit connection with the retention feature 480 oncethe snap head 483 is fully received within the slot 472 to secure theHall board 400. In an embodiment, retention feature 480 is designed toallow the snap-fit connection to be made at approximately the frontsurface of the Hall board 400 so as to avoid adding any length to therear surface of the Hall board 400.

In an embodiment, rear end insulator 222 further includes an inner post487 disposed on one side of the snap post 482 having a flat end surfaceon which the front surface of the Hall board 400 rests when theretention feature 480 makes a snap connection with the snap post 482. Inaddition, in an embodiment, rear end insulator 222 also includes anouter post 488 disposed on the other side of the snap post 482 to engagea radial end wall of the Hall board 400 next to the slot 427.

FIG. 24A depicts a partial perspective view of the Hall board 400,depicting the retention feature 480 for making a snap-fit connectionwith the snap post 482, according to a first embodiment. FIG. 24Bdepicts a partial side cross-sectional view of the Hall board 400 withretention feature 480 in engagement with snap post 482 of the endinsulator 222, according to the first embodiment.

In this embodiment, retention feature 480 further includes a moldedstructure 490 disposed on the front surface of the leg 412 a of the Hallboard 400. In an embodiment, molded structure 490 may be made of resinor plastic-based material provided via overmolding, injection-molding,and similar processes. In an embodiment, molded structure 490 coversHall sensor 450 on the front surface of the leg 412 a of the Hall board400. In an embodiment, molded structure 490 is provided integrally withovermold layer 460 molded in a single step. In an embodiment, moldedstructure 490 includes a lip 492 arranged to engage the undercut portion486 of the snap post 482. In an embodiment, the lip 492 is arranged at adistance from the front surface of the Hall board 400, with at least aportion of the lip 492 covering a portion of the slot 472 along theradial direction. In an embodiment, the lip 492 makes a snap-fitconnection with the snap post 482 proximate the front surface of theHall board 400. In this manner, the snap post 482 is received within theslot 472, but it does not project out of the slot 472 over the rearsurface of the Hall board 400.

FIG. 25A depicts a partial perspective view of the Hall board 400,depicting retention feature 480′ according to a second embodiment. FIG.25B depicts a partial side cross-sectional view of the Hall board 400with retention feature 480′ in engagement with snap post 482 of the endinsulator 222, according to the second embodiment.

In this embodiment, retention feature 480′ includes a molded structure500 similar to the first embodiment described above, but instead of alip provided as a part of the molded structure 500, the molded structure500 supports a metal trap 502. In an embodiment, metal trap 502 includesa U-shaped cross-sectional profile having a main body 504 and two legs506. The legs 506 of the metal trap 502 are mounted on the front surfaceof the Hall board 400 via the molded structure 500. In an embodiment,the main body 504 is arranged at a distance from the front surface ofthe Hall board 400, with at least a portion of the main body 504covering a portion of the slot 472 along the radial direction. In anembodiment, the main body 504 makes a snap-fit connection with the snappost 482 proximate the front surface of the Hall board 400. In thismanner, the snap post 482 is received within the slot 472, but it doesnot project out of the slot 472 over the rear surface of the Hall board400.

FIG. 26 depicts a partial perspective view of the Hall board 400,depicting retention feature 480″ according to a third embodiment. Inthis embodiment, retention feature 480″ includes a molded structure 510similar to the first two embodiments described above, but instead of amolded lip or a U-shaped metal trap, the molded structure 510 supports aplanar place pad 512. In an embodiment, place pad 512 engages a snappost 482″ that includes two laterally projecting side lips 520 on thetop portion 482″ instead of a radially oriented retraction side.

FIG. 27 depicts a perspective view of the place pad 512, according to anembodiment. In an embodiment, place pad 512 is made of sheet metalshaped to include a U-shaped planar body including an inner main body514 and two outwardly projecting legs 516. In an embodiment, the mainbody 514 is secured in contact with the front surface of the Hall board400 along the leg 412 a. The main body 514 is secured against the Hallboard 400 via the overmold structure 510. In an embodiment, the legs 516extend from the main body 514 around the slot 472. Legs 516 includeoppositely arranged snaps 518 that project laterally to cover a portionof the slot 472. In an embodiment, snaps 518 are resiliently flexibleand bendable relative to the legs 516.

FIG. 28A depicts a partial perspective view of the place pad 512 andsnap post 482″, according to an embodiment. In an embodiment, as thesnap post 482″ is moved in the direction of slot 472 of the Hall board400, the snaps 518 of the place pad 512 engage the side lips 520 of thesnap post 482″ and bend upwardly into the slot 472. This is illustratedin the perspective view of FIG. 28B, where the place pad 512 is depictedwithout the snap post 482″. As the snap post 482″ is received within theslot 472, the snaps 518 spring inside valleys 522 formed under the lips520, thus securely engaging the underside of the lips 520. In thismanner, the main body 504 makes a snap-fit connection with the snap post482″ proximate the front surface of the Hall board 400, allowing thesnap post 482″ to be received within the slot 472 without projecting outof the slot 472 over the rear surface of the Hall board 400.

FIG. 29 depicts a partial perspective view of the end insulator 222including a clip post 494, according to an embodiment. In thisembodiment, placement post 493, which is positioned to be receivedwithin the slot 472 of the Hall board 400, does not include a snappingfeature. Instead, clip post 494 provided adjacent the placement post493, with a recess 495 formed facing the placement post 493. Recess 495is designed to engage a clip 496 of the Hall board 400 described below.

FIG. 30 depicts a perspective frontal view of the Hall board 400depicting a fourth embodiment of the retention feature 480′″ in the formof the clip 496. In an embodiment, clip 496 includes a main planar body497 mounted on the front surface of the Hall board 400 and having anopening 498 that aligns with the slot 472 of the Hall board 400. Aengagement edge 499 of the clip 496 extends beyond the radial end wallof the Hall board 400. The clip 496 may be secured to the Hall board 400by, for example, soldering, fastening, or other known method.

FIG. 31A depicts a perspective view of the Hall board 400 secured to theclip post 494 of the rear end insulator 222 via the clip 496, accordingto an embodiment. FIG. 31B depicts a perspective view of the clip 496secured to the clip post 494 of the rear end insulator 222 depictedwithout the Hall board 400, according to an embodiment. In anembodiment, the Hall board 400 is mounted at an angle relative to therear end insulator 222 as the engagement edge 499 of the clip 496 ispositioned within the recess 495 of the clip post 494. The Hall board400 is pivoted around the engagement edge 499 as the placement post 493is received within the opening 498 of the clip 496 and the slot 472 ofthe Hall board 400. Once the fasteners 420 (FIG. 21) are fastened to therear end insulator 222, the placement post 493 and the clip post 494cooperate to structurally support and secure the Hall board 400proximate the leg 412 a.

The above-described embodiments disclose a Hall board designed forsensed brushless DC motor control that does not increase the length ofthe motor. The Hall sensors 450 magnetically sense the magnetic flux ofthe rotor magnet ring 206 as the rotor 204 is rotated. That informationis sent to the controller (not shown), which in turn measures theangular position of the rotor 204 based on the sensor information andcontrols the commutation of the motor according to the angular position.

It should be understood, however, that other aspects and embodiments ofthe invention may be utilized using a motor assembly without a Hallboard, i.e., a BLDC motor that is sensorlessly controlled. Examples ofsensorless motor commutation control are six-step trapezoidalcommutation using the induced motor voltage signals, sinusoidal control,and field-orientated control. Reference is made to U.S. patentapplication Ser. No. 16/896,504 filed Jun. 9, 2020, for a description ofsensorless sinusoidal and field-oriented motor control. Also, referenceis made to U.S. application Ser. No. 16/530,090 filed Apr. 20, 2020, fora description of sensorless motor control using the motor inducedvoltage. An advantage of the Hall board design described in thisdisclosure is that it allows sensed trapezoidal control of a compactmotor that is volumetrically equivalent to a sensorless motor capable ofoutputting the same power performance. However, other aspects of theinvention, for example, the nested support plate, the rotor assembly,and the rear end cap design described below, may be implemented for usewith a sensorless brushless motor.

Another aspect of the invention is described here with reference toFIGS. 32-39.

In the embodiment of FIG. 2 described above, proper alignment of therear motor bearing 258, the rear tool cap 54, and the power tool housing52 may be difficult to achieve. In one implementation, the rear motorbearing 258 is received within the rear tool cap 54, the rotor 204 ismounted within the stator assembly 210, and the motor assembly 200 andrear tool cap 54 sub-assembly is disposed within the clamshells thatform the tool housing 52. The rear tool cap 54 must be fastened to theclamshells of the tool housing 52 against the magnetic force of themagnet ring 206 interacting with stator windings 224, which force therear rotor bearing 54 to be offset with respect to the center axis ofthe motor assembly 200. Moreover, since the housing 52 is often made ofplastic, reliance on the housing 52 for location and alignment the motorassembly 200 relative to rear tool cap 54 and the rear motor bearing 258adds to stack-up tolerances, increases the chance of stack rub, andlimits nominal airgap.

According to an embodiment of the invention, as described below indetail, the rear tool cap of the power tool is designed to support therear motor bearing directly with respect to the stator assembly,independently of the tool housing. In an embodiment, alignment featuresfor piloting and alignment of the stator assembly are added to the reartool cap, allowing the rear tool cap to directly interface with thestator assembly even prior to assembly into the tool housing. By tuningthe rotor bearing pocket of the rear tool cap relative to the statorassembly rather than the housing, concentricity of the rotor outerdiameter to stator inner diameter greatly improves, as the tool housingas well as some motor assembly components do not contribute to radialstack-up.

FIG. 32 depicts a side view of the power tool 70 including an improvedrear tool cap 600 provided for interfacing with the motor assembly 200,according to an embodiment. In an embodiment, power tool 70 includes atool housing 72 that includes two clamshells that come together to houseat least a portion of the motor assembly 200, and rear tool cap 600 ismounted to the end of the housing 72 that also houses a portion of themotor assembly 200. In an embodiment, power tool 70 is similar in manyrespects to power tools 10 and 50 of FIGS. 1 and 2, including atransmission assembly 20 and impact mechanism 50 forward of the motorassembly 200, a handle, etc., the description of which are not repeatedhere.

FIG. 33 depicts a perspective partially exploded view an improved reartool cap 600 provided for interfacing with the motor assembly 200,according to an embodiment. FIG. 34 depicts a perspective view of therear tool cap 600, according to an embodiment. FIG. 35 depicts an axialview of the motor assembly 200 received within the rear tool cap 600,according to an embodiment. FIG. 36 depicts a side cross-sectional viewof the motor assembly 200 received within the rear tool cap 600,according to an embodiment. FIGS. 37 and 38 depict two perspective viewsof the motor assembly 200 received within the rear tool cap 600,according to an embodiment.

As shown in these figures, in an embodiment, the rear tool cap 600includes a radial body 602 that includes a central bearing pocket 604for supporting the rear motor bearing 260, and a peripheral portion 606that is secured to the tool housing 72. Peripheral portion 606 includesa series of receptacles 608 arranged to receive fasteners (not shown)for fastening the rear tool cap 600 to the power tool housing 72. In anembodiment, fan 218 is radially received within the peripheral portion606.

Additionally, in an embodiment, rear tool cap 600 includes one or moreconstraining walls 610 projecting from the peripheral portion 606 aroundthe longitudinal axis around the outer surface of the stator core 212.Constraining walls 610 are arcuately shaped along a circumference thathas a slightly larger diameter than the outer surface of the stator core212. In an embodiment, constraining walls 610 are discretely providedand extend peripherally equidistant from the central bearing pocket 604along the circumference at least partially over the outer surface of thestator core 212. In an embodiment, the tuning pads 616 arecircumferentially distanced from one another to define one or morecircumferential gaps 612 in between. Alternatively, in an embodiment, asingle cylindrical constraining wall 610 may be provided.

In an embodiment, each constraining wall 610 includes one or more tuningpads 616 on its inner surface in contact with the stator core 212.Tuning pads 616 cooperate to form-fittingly and securely receive thestator assembly 210 into the body of the rear tool cap 600. In anembodiment, inner surfaces of the tuning pads 616 are provided along acircumference that has a diameter substantially equal to the diameter ofthe outer surface of the stator core 212.

In an embodiment, the rear motor bearing 260 may be secured within thecentral motor bearing pocket 604 prior to assembly of the rotor 204within the stator assembly 210. Since the tuning pads 616 secure thestator assembly 210 relative to the rear tool cap 600, once the rearmotor bearing 260 is securely received within the central motor bearingpocket 604, the rear portion of the rotor shaft 202 is properly andaccurately piloted relative to the stator assembly 210.

In an embodiment, a series of exhaust vents 618 are provided within therear end cap 600 rearward of the constraining walls 610. Each exhaustvent 618 extends circumferentially along one side of the rear end cap600 between the receptacles 608. Exhaust vents 618 are positioned aroundthe fan 218 in fluid communication with the airflow generated by the fan218 through the motor assembly 200. In an embodiment, fan 218 has asmaller diameter than the diameter of the stator core 212. The airflowgenerated by the fan 218 travels through the motor assembly 200 alonggenerally the longitudinal axis of the motor and is expelled radiallythrough the exhaust vents 618. In an embodiment, on a lower side of therear end cap 600, instead of an exhaust vent, a lower opening 614 isprovided that aligns with and receives the first connector 404 of themotor assembly 200.

In an embodiment, as best seen in FIGS. 36-38, the tuning pads 616 mayextend along the outer surface of the stator assembly 210 fromapproximately half of the length of the stator core 212 up to nearly thefull length of the stator assembly 210 to fully contain the statorassembly 210 within the rear tool cap 600. This allows the motorassembly 200 to be secured within the rear tool cap 600 prior toassembly of the rear tool cap 600 to the tool housing 72. In anembodiment, as shown in FIG. 32, the clamshells of the tool housing 72may accordingly be sized to only cover less than half the length of thestator assembly 210.

This arrangement significantly eases the manufacturing process, as alltransmission assembly 20 components can be assembled into the toolhousing 72 prior to assembly of the rear tool cap 600 together with themotor assembly 200 and the support plate 230 into the tool housing 72.To complete this process, the motor assembly 200 may be coupled to thetransmission assembly 20 by locating the cam carrier bearing 32 withinthe second bearing pocket 236 of the support plate 230 as the rear toolcap 600 is fastened to the clamshells of the tool housing 72. Thisarrangement, in combination with the features of the motor assembly 200and support plate 230 discussed above, contributes to reduction in theoverall length of the power tool 50.

Referring to FIGS. 39-41, an alternative rear tool cap 700 is describedherein according to an embodiment.

FIG. 39 depicts a perspective view of rear tool cap 700, according to anembodiment. FIG. 40 depicts an axial view of the motor assembly 200mounted on the rear tool cap 700, according to an embodiment. FIG. 41depicts a side cross-sectional view of the motor assembly 200 mounted onthe rear tool cap 700, according to an embodiment.

Similar to rear tool cap 600, the rear tool cap 700 of this embodimentincludes a radial body 702 that includes a central bearing pocket 704for supporting the rear motor bearing 260, and a peripheral portion 706that is secured to the tool housing 72. Peripheral portion 706 includesa series of receptacles 708 arranged to receive fasteners (not shown)for fastening the rear tool cap 700 to the power tool housing 72. Unlikerear tool cap 600, however, in an embodiment, instead of circumferentialturning pads disposed around the outer surface of the stator assembly210, the rear tool cap 700 includes axial posts 702 projecting axiallyfrom the radial body 702 arranged to be received within the slots of thestator assembly 210 formed circumferentially between stator windings224. Axial posts 702 are designed to penetrate the slots of the statorassembly 210 in contact with a portion of the stator core 212 and/or thestator teeth 214 to provide radial support for the rear tool cap 700,and therefore the central bearing pocket 704, relative to the statorassembly 210. In an embodiment, axial posts 720 extend throughapproximately the full length of the stator core 212.

In an embodiment, each axial post 702 may include an outer edge 712 andan outer edge 714 that is radially inward of the inner edge 712. In anembodiment, inner edges 712 are arranged to come into contact with theinner diameter of the stator core 212. Additionally, and/oralternatively, outer edges 714 are arranged to come into contact withadjacent tips of stator teeth 214. In this manner, the rear tool cap 700is supported with respect to the stator assembly 210 independently ofthe power tool housing 72. Reference is once again made to US PatentPublication No. 2017/0294819A1, which is incorporated herein byreference in its entirety, for a description of the axial posts 710 forpiloting and support of a bearing support structure such as the reartool cap 700, and consequently the rotor 204, relative to the statorassembly 210. In an embodiment, a series of six axial posts 710 may beprovided, though as little as three axial posts 710 can sufficientlysupport the rear tool cap 700 relative to the stator assembly 210.

In an embodiment, to accommodate insertion of the axial posts 710 intothe stator slots, Hall board 400 may also be provided forward of themotor assembly 200 opposite the rear tool cap 700. Additionally, in anembodiment, the fan 218 is positioned forward of the motor assembly 200between the Hall board 400 and the transmission assembly 20. In anembodiment, annular recess 216 of the rotor 204 is provided facing therear tool cap 700 to receive the rear motor bearing 260 and centralbearing pocket 704 of the rear tool cap 700 therein. In this embodiment,a radial plane B intersects at least a portion of the central bearingpocket 704, the magnet ring 206, the stator windings 224, and the axialposts 710.

In an embodiment, the rear motor bearing 260 may be secured within thecentral bearing pocket 704 of the rear tool cap 700 prior to assembly ofthe rotor 204 within the stator assembly 210. As the axial posts 710 arereceived relative to the stator slots, the rear portion of the rotorshaft 202, and thus the rotor 204 as a whole, is piloted relative to thestator assembly 210.

Each of the above described power tools is compact in both axial lengthand girth. For example, the impact power tools 10, 50 and 70 each mayhave an overall axial length L5, L6, L7 from the rear end portion of thehousing 12, 52, 72 to a front end of the tool holder 28 of less than orequal to approximately 110 mm (e.g., approximately 96 mm to 110 mm, suchas approximately 106 mm for power tool 10 or approximately 101 mm forpower tools 50 and 70). In addition, an axial distance L2, L4 betweenthe rear plate of the cam carrier 22 and the front plane 124, 244 of themotor envelope 120, 240 is less than approximately 10 mm (e.g.,approximately 7 mm to 10 mm, such as approximately 9.1 mm for power tool10) and may be less than approximately 4 mm (e.g., approximately 2 mm to4 mm, such as approximately 3.1 mm for power tool 50).

At the same time, the above-described power tools 10, 50 and 70 areconfigured to produce a maximum power output (measured in Max Watts Outor MWO) of at least approximately 450 Watts (e.g., approximately 450 to550 Watts, such as at least approximately 450 Watts or at leastapproximately 480 Watts). The above described power tools 10, 50 and 70also can produce a maximum output torque of at least approximately 1800inch-pounds (e.g., approximately 1800 to 2010 inch-pounds, such as atleast approximately 1825 inch-pounds).

Thus, the above-described power tools 10, 50 and 70 produce much greaterpower and torque for their compact size than what is commerciallyavailable or has otherwise been achieved previously. For example, theabove described power tools 10, 50 and 70 have a ratio of power outputto tool length of at least approximately 4.5 Watts/mm (e.g.,approximately 4.5 to 5.0 Watts/mm (e.g., approximately 4.5 Watts/mm (forpower tool 10) or approximately 4.8 Watts/mm (for power tool 50)). Theabove described power tools 10, 50 and 70 also have a ratio outputtorque to tool length of at least approximately 18.0 inch-pounds/mm(e.g., approximately 18.0 inch-pounds/mm to 18.9 inch-pounds/mm, such asapproximately 18.0 inch-pounds/mm (for power tool 10) or approximately18.1 inch-pounds/mm (for power tool 50)). Other exemplary power toolswithin the scope of the above disclosure are set forth in the belowtable:

Motor Max Dia- Motor Max Torque Tool Power/ Torque/ meter Length Power(inch- Length Tool Tool (mm) (mm) (Watts) pounds) (mm) Length LengthExample 1 46 17 450 1825  96 4.7 19.0 Example 2 51 18 480 1910 106 4.518.0 Example 3 51 18 480 1825 101 4.8 18.1 Example 4 56 20 528 2008 1104.8 18.3

Example embodiments have been provided so that this disclosure will bethorough, and to fully convey the scope to those who are skilled in theart. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Terms of degree such as “generally,” “substantially,” “approximately,”and “about” may be used herein when describing the relative positions,sizes, dimensions, or values of various elements, components, regions,layers and/or sections. These terms mean that such relative positions,sizes, dimensions, or values are within the defined range or comparison(e.g., equal or close to equal) with sufficient precision as would beunderstood by one of ordinary skill in the art in the context of thevarious elements, components, regions, layers and/or sections beingdescribed.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A power tool comprising: a housing having arearward end portion and a forward end portion; a brushless motorreceived in the housing, the motor including a rotor configured torotate about a rotor axis and a stator assembly having a stator core andconductive windings, the motor defining a motor envelope bounded by arear plane at a rearmost point of the stator assembly and the rotor, afront plane at a frontmost point of the stator assembly and the rotor,and a generally cylindrical boundary extending from the rear plane tothe front plane and surrounding a radially outermost portion of thestator assembly and the rotor; a rotor shaft extending along the rotoraxis and coupled to and configured to be rotatably driven by rotation ofthe rotor; a transmission received in the housing and including an inputmember coupled to and configured to be rotatably driven by rotation ofthe rotor shaft, and an output member configured to be driven byrotation of the input member; a first bearing configured to support therotor shaft and at least partially received within the motor envelope;and a second bearing configured to support a component of thetransmission and at least partially received within the motor envelope.2. The power tool of claim 1, wherein the transmission comprises aplanetary gear set with a sun gear rotatably driven by the rotor shaft,a carrier, at least one planet gear rotatably mounted to the carrier andmeshed with the sun gear, and a ring gear meshed with the at least oneplanet gear.
 3. The power tool of claim 2, wherein the second bearingsupports the carrier.
 4. The power tool of claim 1, further comprising athird bearing configured to support the rotor shaft.
 5. The power toolof claim 4, wherein the rearward end portion of the housing defines arecess and the third bearing is disposed at least partially in therecess.
 6. The power tool of claim 1, further comprising a support plateconfigured to support a portion of the transmission.
 7. The power toolof claim 6, wherein the support plate includes a nested portion that isat least partially received within the motor envelope.
 8. The power toolof claim 7, wherein the nested portion of the support plate supports atleast one of the first bearing and the second bearing.
 9. The power toolof claim 7, wherein the nested portion of the support plate is at leastpartially received within a recess in the rotor.
 10. The power tool ofclaim 1, wherein the first bearing is received at least partially withina recess in the rotor.
 11. The power tool of claim 1, further comprisinga rotational impact mechanism coupled to the output member of thetransmission and to an output spindle, the impact mechanism configuredto transmit continuous rotary motion without impacts from thetransmission to the output spindle when a torque on the output spindledoes not exceed a transition torque, and to transmit rotational impactsfrom the motor to the output spindle when a torque on the output spindleexceeds the transition torque.
 12. The power tool of claim 11, whereinthe power tool has a maximum power output of at least 430 Watts, alength of the tool from a rear end of the housing to a front end of theoutput spindle of less than or equal to 110 mm, and a ratio of themaximum power output of the motor to the length of the tool is at least4.5 Watts/mm.
 13. The power tool of claim 11, wherein the power tool hasa maximum output torque of at least 1820 inch-pounds, a length of thetool from a rear end of the housing to a front end of the output spindleof less than or equal to 110 mm, and a ratio of the maximum outputtorque of the tool to the length of the tool is at least 18.0inch-pounds/mm.
 14. A power tool comprising: a housing having a rear endportion and a front end portion; a brushless motor received in thehousing, the motor including a rotor configured to rotate about a rotoraxis and a stator assembly having a stator core and conductive windings,the motor defining a motor envelope bounded by a rear plane at arearmost point of the stator assembly and the rotor, a front plane at afrontmost point of the stator assembly and the rotor, and a generallycylindrical boundary extending from the rear plane to the front planeand surrounding a radially outermost portion of the stator assembly andthe rotor; a rotor shaft extending along the rotor axis and coupled toand configured to be rotatably driven by rotation of the rotor; atransmission received in the housing and including an input memberconfigured to be rotatably driven by rotation of the rotor shaft, anoutput member configured to be driven by rotation of the input member;and a support plate configured to support at least a portion of thetransmission, wherein the support plate is held non-rotatably relativeto the housing and has a rearward portion at least partially nestedwithin the stator assembly.
 15. The power tool of claim 14, wherein atleast a portion of the rearward portion of the support plate is at leastpartially received within the rotor.
 16. The power tool of claim 14,further comprising a first bearing configured to support the rotor shaftand a second bearing configured to support one of the rotor shaft and aportion of the transmission, wherein each of the first bearing and thesecond bearing are at least partially nested within the stator assembly.17. The power tool of claim 16, wherein the transmission comprises aplanetary gear set with a sun gear rotatably driven by the rotor shaft,a carrier, at least one planet gear rotatably mounted to the carrier andmeshed with the sun gear, and a ring gear meshed with the planet gear,wherein the second bearing is configured to support the carrier.
 18. Thepower tool of claim 14, wherein the second bearing is configured tosupport the output member of the transmission and further comprising athird bearing configured to support the rotor shaft.
 19. The power toolof claim 18, wherein the rearward end portion of the housing defines arecess and the third bearing is disposed at least partially in therecess.
 20. The power tool of claim 14, further comprising an outputspindle configured to be driven by the transmission, wherein the powertool has a maximum power output of at least 430 Watts, a length from arear end of the housing to a front end of the output spindle of lessthan or equal to 110 mm, and a ratio of the maximum power output of themotor to the length of the tool is at least 4.5 Watts/mm.